Conductive adhesive agent, packaging structure, and method for manufacturing the same structure

ABSTRACT

A conductive adhesive agent of the invention contains an elution preventing film-forming agent  4,  which becomes reactive after electric continuity through a conductive particle  3  appeared in the conductive adhesive agent when a binder resin  2  is being hardened, to thereby form an elution preventing film  5  on a surface of the conductive particle  3.  By using this conductive adhesive agent, the packaging structure is made migration resistant and sulfurization resistant.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a conductive adhesive agent used in joining ofan electronic element and a printed-circuit board in a field ofpackaging of the electronic element, a packaging structure using theconductive adhesive agent, and a method for manufacturing the packagingstructure.

2. Description of the Related Art

Recently, high consciousness for environmental harmonies has started torestrict use of lead contained in a solder alloy in the field ofpackaging of electronic devices, thus leading to an emergent need forestablishment of technologies of joining electronic elements using amaterial in which lead is not contained.

As a lead-free packaging technology is known the one using a lead-freesolder and a conductive adhesive agent. Recently, however, more and moreattention is attracted to a conductive adhesive agent expected to havemerits such as flexibility of a joining portion and lower packagingtemperature.

A conductive adhesive agent generally has conductive particles dispersedin a resin-based adhesive component. To package a device, first aconductive adhesive agent is applied on a board electrode, the device isattached thereon, and then the resin is hardened. By this process, thejoining portions are adhered to each other by the resin and also theconductive particles come in contact with each other as the resinshrinks, thus ensuring continuity at the joint.

The resin of a conductive adhesive agent has a hardening temperature ofabout 150° C., which is very low as compared to a melting temperature ofabout 240° C. required for soldering, thus qualifying that agent for useeven in packaging of such inexpensive devices that have a low heatresistance.

Also, the joining portions are adhered to each other by a resin, thusbeing able to flexibly accommodating a deformation due to heat or anexternal stress. This gives the conductive adhesive agent a merit thatthe joining portions adhered thereby is not liable to have cracks ascompared to those adhered by solder which is an alloy.

For the above reasons, the conductive adhesive agent is expected as analternative of solder.

Silver, generally used as conductive particles of a conductive adhesiveagent, has such a characteristic that it is subject to easy ionmigration or sulfurization, problem of which must be solved to put theconductive adhesive agent to practical use as an alternative materialfor solder.

First, ion migration is described as follows. A phenomenon of ionmigration is a sort of electrolytic action, by which dielectricbreakdown occurs between electrodes along the following four steps whenan electrolyte such as water is present between the electrodes underapplication of voltage:

Step 1: An anode metal is eluted and ionized;

Step 2: The ionized metal migrates toward a cathode under application ofvoltage;

Step 3: The metal ions which have migrated to the cathode areprecipitated; and

Step 4: Steps 1 through 3 are repeated.

Such a phenomenon of ion migration causes the metal to grow in a treeshape between the electrodes, finally bridging the gap between theelectrodes, resulting in dielectric breakdown.

Silver used as a conductive filler of a conductive adhesive agent iseasily eluted, thus bringing about ion migration. Further, a recenttrend for further reduction in size and weight of electronic equipmenthas narrowed a pitch between electrodes formed in a semiconductor devicean electronic element or on a printed-circuit board, thus further easilycausing ion migration. Taking this into account, the problem of ionmigration must be solved indispensably to put to practical use thepackaging technology by use of a conductive adhesive agent.

There have conventionally made such three proposals that inhibit ionmigration:

Proposal 1: Alloying of conductive filler (e.g., alloying of silver andcopper or silver and palladium);

Proposal 2: Sealing of conductive adhesive agent by use of insulatingresin such as epoxy resin; and

Proposal 3: Capturing eluted metal ions and rendering them insolublematerial by addition of ion capturing agent such as ion exchange resinor chelating agent to conductive adhesive agent

Those proposals, however, have the following disadvantages. Proposal 1requires a very expensive filler metal, thus increasing a cost of theconductive adhesive agent. Proposal 2 needs to add an extra step ofsealing to thereby increase the number of required steps or greatlyexpand provisions, thus increasing the manufacturing costs. Proposal 3causes a metal ion to be eluted from the conductive filler to therebydeteriorate contact-ness of the conductive filler, thus raising theconnection resistance.

Thus the above-mentioned proposals have indeed an effect of inhibitingion migration but also have various problems and so are difficult to putto practical use except in a special application field.

Next, a phenomenon of sulfurization is described as follows.Sulfurization refers to such a phenomenon that a metal reacts with aweal acidic air containing a sulfuric content such as hydrogen sulfideor sulfur dioxide to provide such a material with low conductivity thatis called a metal sulfide. Although sulfurization is not know enoughyet, it is considered to occur along the following steps:

Step 1: A metal is eluted and ionized in a weak acidic atmosphere; and

Step 2: the metal ions react with sulfur ions to generate a metalsulfide.

As described above, a conductive filler is mainly made up of silver butis liable to be sulfurized, so that when silver is sulfurized,volume-specific resistance of the conductive adhesive agent rises, whichis accompanied by a rise in the connection resistance. Few solutions forthis problem have been reported so far, so that a packaging structureusing a conductive adhesive agent cannot be applied to a product havingan electronic element which may be used in such an environment assurroundings of a hot spring or volcano, in which hydrogen sulfide orsulfide dioxide is present at a relatively high concentration. Thisgreatly restrict application fields of the packaging structure using aconductive adhesive agent.

SUMMARY OF THE INVENTION

In view of the above, it is an object of the invention to provide such apackaging structure using a conductive adhesive agent that is capable ofmaintaining a reliability even under a very humid condition or such asevere condition as a gaseous atmosphere containing sulfur.

To this end, a conductive adhesive agent according to the invention hasa binder resin, a conductive particle, and an elution preventing-filmforming agent, which forming agent becomes reactive after electricalcontinuity through the conductive particle is established in thisconductive adhesive agent when the binder resin is hardened, thusforming an elution preventing film on the surface of the conductiveparticle. This causes the following to occur.

When the surface of the conductive particle is coated with the elutionpreventing film, the conductive particle can be prevented from beingeluted even if it is left in a hot and humid environment or in a gascontaining sulfur. Therefore, the elution preventing film can prevention migration as well as the above-mentioned first step ofsulfurization. Thus, the conductive adhesive agent according to theinvention can be used to manufacture a packaging structure not liable toencounter ion migration and sulfurization.

When, in this case, the elution preventing film is made of an insulatingmaterial and if it is present at a site related to conduction (i.e.,contact point between conductive particles and that between a conductiveparticle and an electrode or the like), it inhibits electricalcontinuity, thus leading to such a disadvantage that raises a connectionresistance of the packaging structure.

By the conductive adhesive agent according to the invention, on theother hand, no elution preventing film is formed on the conductiveparticle until that adhesive agent is hardened, so that only after theconductive particles come in contact with each other in the process ofhardening, the elution preventing film is formed on the particlesurface. Accordingly, the elution preventing film is not formed at asite related to continuity, thus avoiding a rise in the connectionresistance.

If the above-mentioned requirement of the invention is not met, on theother hand, the object of the invention cannot be realized. That is,when an elution preventing film is formed on the conductive particlesbefore continuity is established, that is, before the agent is hardened,the elution preventing film is already present at a site related tocontinuity when the conductive adhesive agent is hardened to therebyinhibit electrical continuity, thus raising the connection resistance.

For the conductive adhesive agent according to the invention, preferablythe reactive temperature of the elution preventing film-forming agentsatisfy the following conditions:

application temperature of conductive adhesive agent<reactivetemperature of elution preventing-film forming agent;

and

reactive temperature of elution preventing film-forming agent≦hardeningtemperature of binder resin.

When these conditions are established, the following will occur.

No elution preventing film is formed when a conductive adhesive agentaccording to the invention is applied. When the conductive adhesiveagent starts to be heated to its hardening temperature, the elutionpreventing film-forming agent becomes reactive at a temperature rangebefore the hardening to thereby form an elution preventing film on theconductive particle. At this point in time, the binder resin is nothardened yet so does not inhibit the formation of the elution preventingfilm. Therefore, the elution preventing film is formed uniformlyeverywhere on the conductive particle surfaces except on a contact pointbetween the conductive particle and any other conductive substances (anyother conductive particles or electrodes). When the elution preventingfilm is formed and then the conductive adhesive agent is heated up toits hardening temperature, the binder resin is hardened to completeconnective fixation by the conductive adhesive agent.

Also, for the conductive adhesive agent according to the invention, theelution preventing film-forming agent contains a chelating agent, whichpreferably becomes reactive after electrical continuity through theconductive particles is established in this conductive adhesive agentwhen the binder resin is hardened, thus forming an elution preventingfilm containing a metallic complex on the conductive particle. Then, thefollowing will occur.

Since the elution preventing film-forming agent contain a chelatingagent, an elution preventing film containing a very stable material ofmetallic complex is formed on the conductive particle. Accordingly, evenif a connection site given by the conductive adhesive agent is left in ahot and humid environment or in a gas containing sulfur, the conductiveparticle is not eluted.

Also, if a metallic complex, which is an insulating material, is presentat a site related to continuity (contact point between conductiveparticles or between a conductive particle and an electrode), theelectrical continuity is inhibited, thus raising the connectionresistance of the packaging structure. As for a conductive adhesiveagent according to the invention, on the other hand, no metallic complexis formed on the conductive particle before the conductive adhesiveagent is hardened, so that only after the conductive particles come incontact with each other to establish continuity in the hardening step,the elution preventing film containing the metallic complex is formed onthe particles. Thus, the elution preventing film containing a metalliccomplex is not formed at the site related to continuity, thus avoiding arise in the connection resistance.

Also, to contain a chelating agent in an elution preventing film-formingagent for the conductive adhesive agent according to the invention,preferably the activation temperature of the chelating agent satisfiesthe following conditions:

application temperature of conductive adhesive agent<activationtemperature of chelating agent;

and

activation temperature of chelating agent≦hardening temperature ofbinder resin.

Then, the following will occur.

A chelating agent is a material which selectively reacts with a metal toform a metallic complex, which reaction is most liable to occur at anactivation temperature of the chelating agent. Since the activationtemperature is higher than an application temperature of the conductiveadhesive agent and equal to or lower than a hardening temperature of thebinder resin, it reacts with a metal at a temperature therebetween tothereby form an elution preventing film containing the metallic complexon the conductive particles. Therefore, before the conductive adhesiveagent is hardened, the chelating agent is dispersed in the conductiveadhesive agent, so that an elution preventing film is little formed onthe conductive particle. Then, in the hardening step, the chelatingagent reacts with the conductive particle to form the elution preventingfilm containing a metallic complex on the particle surfaces. Thiselution preventing film provides a protecting film for the conductiveparticle, thus inhibiting ion migration and sulfurization. Also, theelution preventing film is formed after continuity is established, sothat the elution preventing film (metallic complex) is hardly formed ata site related to continuity, thus suppressing a rise in the connectionresistance.

An activation temperature (reaction temperature) here refers to atemperature at which a chelating agent and a metal react with each othermost frequently, generally coming near the melting temperature. Notehere that the relation between the reaction between a chelating agentand a metal and the temperature is nonlinear in that at the activationtemperature, the reaction is rapidly activated and at a temperature fardistant from that, the reaction occurs little.

An application temperature of the conductive adhesive agent refers to aworking temperature at which the conductive adhesive agent is applied ona board electrode by printing or using a dispenser in order tomanufacture a packaging structure. The application temperature generallycomes near room temperature of 20-40° C. or so.

If as the chelating agent is employed such a material that has anactivation temperature higher than the hardening temperature of thebinder resin (e.g., bismthyol II having a melting temperature of 246° C.as against a hardening temperature of 150° C.), the chelating agent doesnot react with the conductive particle even after hardening, so that nometallic complex is formed, thus failing to obtain the effects ofresisting against ion migration and sulfurization.

Since the activation temperature is often near the melting temperature,as the chelating agent may be used, for example, an anthranilic acid(melting point: 145° C.), thionylide (217° C.), or pyrogallol (132° C.)as against such a conductive adhesive agent that has an applicationtemperature of 25° C. and a hardening temperature of 150° C.

As for the conductive adhesive agent according to the invention, theelution preventing film-forming agent is encapsulated in amicro-capsule, so that preferably the melting temperature of thismicro-capsule and the activation temperature of the chelating agentcontained in the elution preventing film-forming agent satisfy thefollowing conditions:

application temperature of conductive adhesive agent<melting temperatureof macro-capsule;

melting temperature of micro-capsule≦hardening temperature of binderresin;

and

activation temperature of chelating agent≦hardening temperature ofbinder resin.

When those conditions are satisfied, not only the connection resistanceof the packaging structure after hardening is inhibited but also morechelating agents can be selected. The reasons are explained below.

In this improvement, a chelating agent as encapsulated in amicro-capsule is added to the conductive adhesive agent to therebyinhibit the reaction of the unhardened chelating agent even moresecurely. The reasons are described as follows.

By the configuration according to the invention, the activationtemperature of the chelating agent is higher than the applicationtemperature of the conductive adhesive agent, so that the reactivity ofthe chelating agent is low before the binder resin is hardened yet.However, a water content, a hardening agent (amine, acid anhydride, orthe like) a residual impurity given in production of a binder resin(chloride, or the like), or the like serves as a reaction accelerator,so that the chelating agent is actually reactive even before hardening,thus forming an elution preventing film containing a metallic complex onthe conductive particle surfaces.

As for a conductive adhesive agent according to the invention improvedas mentioned above, on the other hand, the chelating agent is protectedin a micro-capsule, so that the chelating agent reacts little before thebinder agent is hardened. When the binder agent starts to be hardened,the micro-capsule melts to thereby release the chelating agent, whichthen reacts with the conductive particle to thereby form an elutionpreventing film containing a metallic complex. Thus, by the inventionimproved as mentioned above, the elution preventing film (metalliccomplex) is further less formed before the binder resin is hardened,thus securely inhibiting a rise in the connection resistance in theconductive adhesive agent after hardening. Further, since the activationtemperature of the chelating agent may well be lower than theapplication temperature of the conductive adhesive agent, the requiredproperties (especially activation temperature) of the chelating agentbecome more lenient, thus enabling selecting more chelating agents thatmuch.

As for the conductive adhesive agent according to the invention,preferably the elution preventing film-forming agent is made up of awater-insoluble material. Then, the following will occur.

Since the elution preventing film, once formed, does not solve out in ahot and humid environment, the in migration resistance is enhanced. Theinsoluble-ness is here defined that an insolubility (weight soluble in100 g of water) is less than 1×10⁻⁵ g.

As for a conductive adhesive agent according to the invention,preferably the elution preventing film-forming agent is made up of amaterial insoluble in a aqueous solution containing a hydrogen sulfideor sulfur oxide. Then, the following will occur. That is, since theelution preventing film, once formed, does not solve out in a weak acidaqueous solution or atmosphere containing sulfur, ion migrationresistance and sulfurization resistance are enhanced.

As for a conductive adhesive agent according to the invention,preferably the elution preventing film-forming agent as dispersed in anon-polar solvent is added to this conductive adhesive agent. Then, thefollowing will occur.

Since the non-polar solvent serves to inhibit the reaction of thechelating agent, in the conductive adhesive agent according to theinvention improved as mentioned above, the chelating agent is reactivelittle before the binder resin is hardened. When the binder resin startsto be hardened, the chelating agent reacts with the conductive particleto thereby form an elution preventing film containing a metalliccomplex. Thus, by the invention improved as mentioned above, the elutionpreventing film (metallic complex) is formed further less before thebinder resin is hardened, thus securely inhibiting a rise in theconnection resistance in the conductive adhesive agent. Further, theactivation temperature of the chelating agent may well be lower than theapplication temperature of the conductive adhesive agent, so that therequired properties (especially activation temperature) of the chelatingagent become more lenient, thus enabling selecting more chelating agentsthat much.

Also, to achieve the above-mentioned object, the packaging structureaccording to the invention includes an electric structure and aconductive adhesive agent layer formed on the electric structure in sucha configuration that the conductive adhesive agent layer containsconductive particles and is coated with an elution preventing filmexcept a contact point between these conductive particles and betweenthe conductive particle and the electric structure.

This improves the ion migration resistance. This is because the elutionpreventing film, which provides a protecting film against ion migration,is formed on a necessary portion, that is, a portion except thoserelated to continuity.

A packaging structure has another electric structure disposed on theabove-mentioned one, so that these electric structures are electricallyinterconnected, the conductive adhesive agent layer has a very largeeffect on the connection resistance because of an ion migrationreaction, or the like. To guard against this, the invention is appliedto such a configuration so as to have a large effect.

In a packaging structure according to the invention, preferably theelution preventing film s made up of a material containing a metalliccomplex. Then, the following will occur. That is, since an elutionpreventing film containing a metallic complex, which is very stable inproperty, is formed on the conductive particle, the conductive particledoes not solve out even if a site connected by the conductive adhesiveagent is left in a hot and humid environment or in a gas containingsulfur.

Also, if a metallic complex, which is an insulating material, is at asite related to continuity (contact point between conductive particlesor between a conductive particle and an electrode), electricalcontinuity is deteriorated, thus increasing the connection resistance ofthe packaging structure. A packaging structure of the invention asimproved above, on the other hand, has no metallic complex formed at asite related to continuity, thus avoiding to increase the connectionresistance.

In the packaging structure of the invention, preferably the elutionpreventing film is made up of a water-insoluble material. Then, theelution preventing film once formed dies not solve out even in a hot andhumid environment, thus enhancing the ion migration resistance.

In the packaging structure of the invention, preferably the elutionpreventing film is made up of a material not soluble in an aqueoussolution containing hydrogen sulfide or sulfur oxide. Then, thefollowing will occur. That is, the elution preventing film once formeddoes not solve out even in a weak acid aqueous solution or an atmospherecontaining sulfur, thus enhancing the ion migration resistance and thesulfurization resistance.

To manufacture such a packaging structure of the invention as mentionedabove, the following two methods are available.

A first method prepares such a conductive adhesive agent that contains abinder resin, a conductive particle, and an elution preventingfilm-forming agent, a reaction temperature of which elution preventingfilm-forming agent satisfies the following conditions:

application temperature of conductive adhesive agent<reactiontemperature of elution preventing film-forming agent;

and

reaction temperature of elution preventing film-forming agent≦hardeningtemperature of binder resin,

the method comprising:

a conductive adhesive agent forming step of applying and forming theconductive adhesive agent on the electrode at the applicationtemperature;

an elution preventing film-forming step of heating the conductiveadhesive agent up to the hardening temperature and also permitting theelution preventing film-forming agent to react at the reactiontemperature before that hardening temperature is reached to thereby forman elution preventing film on the conductive particle; and

a hardening step of heating the conductive adhesive agent up to thehardening temperature to harden the binder resin.

A second method prepares such a conductive adhesive agent that containsa binder resin, a conductive particle, and an elution preventingfilm-forming agent, reaction temperature of which elution preventingfilm-forming agent satisfies the following conditions:

 hardening temperature of binder resin<reaction temperature of elutionpreventing film-forming agent,

the method comprising:

a conductive adhesive agent forming step of forming a layer of theconductive adhesive agent as unhardened on the electrode;

a hardening step of heating the conductive adhesive agent up to thehardening temperature to thereby harden the binder resin; and

an elution preventing-film forming step of re-heating the conductiveadhesive agent to the reaction temperature or higher to thereby permitthe elution preventing film-forming agent to be reactive, thus formingan elution preventing film on the conductive particle.

By those manufacturing methods, the following will occur.

That is, when a conductive adhesive agent according to the invention, noelution preventing film is formed. Then, when the conductive adhesiveagent is heated to its hardening temperature, at a temperature before itis hardened, the elution preventing film-forming agent becomes reactiveto thereby form an elution preventing film on the conductive particle.At this point in time, the binder resin is not hardened yet, thusavoiding inhibiting the formation of the elution preventing film.Therefore, the elution preventing film is uniformly formed everywhere onthe conductive particle surfaces except on a contact point between theconductive particle and any other conductive materials (any otherconductive particles or electrodes, or the like). Then, when thehardening temperature of the conductive adhesive agent is reached afterthe elution preventing film is formed, the binder resin is hardened,thus completing the connection fixation by the conductive adhesiveagent.

By the second method, a rise in the connection resistance of thepackaging structure can be inhibited further securely. The reason is asfollows.

Since the reaction temperature of the elution preventing film-formingagent is higher than the hardening temperature of the binder resin,before the conductive adhesive agent is hardened and when it is beinghardened, the elution preventing film-forming agent forms no elutionpreventing film on the conductive particle surfaces, thus providing goodcontinuity. Then, the binder resin, after being hardened, can bere-heated up to a temperature higher than the reaction temperature ofthe elution preventing film-forming agent to thereby form an elutionpreventing film only at a site not related to continuity. Accordingly,the connection resistance of the packaging structure after hardening canbe inhibited securely.

Also, preferably the first method prepares the elution preventingfilm-forming agent which contains a chelating agent, activationtemperature of which satisfies the following conditions:

application temperature of conductive adhesive agent<activationtemperature of chelating agent;

and

activation temperature of chelating agent≦hardening temperature ofbinder resin,

during the elution preventing film forming step, the conductive adhesiveagent being heated up to the hardening temperature so that at theactivation temperature before that temperature is reached the chelatingagent is made reactive to thereby form an elution preventing filmcontaining a metallic complex on the conductive particle. Then, thefollowing will occur.

The chelating agent selectively reacts with a metal to form a metalcomplex, which reaction occurs most at the activation temperaturethereof. This improved manufacturing method uses a chelating agent andsets its activation temperature higher than the application temperatureof the conductive adhesive agent and not higher than the hardeningtemperature of the binder resin. Accordingly, the chelating agentbecomes reactive at a temperature between the application temperature ofthe conductive adhesive agent and the hardening temperature of thebinder resin to thereby form an elution preventing film containing ametallic complex on the conductive particle. Therefore, before theconductive adhesive agent is hardened, the chelating agent is dispersedin the conducive adhesive agent, thus scarcely forming an elutionpreventing film on the conductive particle surfaces. When it starts tobe hardened, the chelating agent reacts with the conductive particle toform an elution preventing film containing a metallic complex on theparticle surfaces. This elution preventing film provides a protectingfilm for the conductive particle, thus inhibiting ion migration andsulfurization. Also, since the elution preventing film is formed aftercontinuity is established, the elution preventing film (metalliccomplex) is hardly formed at a site related to continuity, thussuppressing a rise in the connection resistance.

Preferably the second method prepares the elution preventingfilm-forming agent which contains a chelating agent which has anactivation temperature higher than the hardening temperature of thebinder resin, in which:

At the hardening step, the binder resin is hardened by a heating processat a temperature lower than the activation temperature; and

at the elution preventing film forming step, the conductive adhesiveagent is re-heated up to a temperature not less than the activationtemperature to act with the chelating agent, thus forming an elutionpreventing film containing a metallic complex on the conductiveparticle. Then, it is possible to form the elution preventing film thatcontains a metallic complex.

Preferably the second method prepares the elution preventingfilm-forming agent that is encapsulated in a micro-capsule, so that themelting temperature of this micro-capsule and the activation temperatureof the chelating agent containing the elution preventing film satisfythe following conditions:

application temperature of conductive adhesive agent<melting temperatureof micro-capsule;

melting temperature of micro-capsule≦hardening temperature of binderresin;

and

activation temperature of chelating agent≦hardening temperature ofbinder resin,

then, a larger number of the conductive adhesive agents can be selectedoptionally. The reason is as follows.

Since the melting temperature of the micro-capsule is higher than thehardening temperature of the conductive adhesive agent, before thebinder resin is hardened or when it is being hardened, the elutionpreventing film-forming agent does not form an elution preventing filmon the conductive particle surfaces, thus providing good continuity.Then, when the binder resin is hardened and re-heated to a temperaturehigher than the melting temperature of the micro-capsule, an elutionpreventing film-forming is released from the micro-capsule to therebyform an elution preventing film only at a site not related tocontinuity. Accordingly, it is possible to more securely lower theconnection resistance of the packaging structure after hardening. Also,it is not necessary to set the reaction temperature of the elutionpreventing film-forming agent at a temperature higher than the hardeningtemperature of the binder resin, a larger number of the elutionpreventing film-forming agents can be selected optionally.

Preferably the first and second methods uses such a conductive adhesiveagent that the elution preventing film-forming agent is added to thisconductive adhesive agent as dispersed in a non-polar solvent. Then, thefollowing will occur.

Since the non-polar solvent serves to inhibit the reaction of thechelating agent, the elution preventing film-forming agent added to theconductive adhesive agent as dispersed in the non-polar solvent causesthe chelating agent to be reactive little before the binder resin ishardened. Then, when the binder resin starts to be hardened, thechelating agent reacts with the conductive particle to form an elutionpreventing film containing a metallic complex. Accordingly, the elutionpreventing film (metallic complex) is formed further less before thebinder resin is hardened, thus securely inhibiting a rise in theconnection resistance in the conductive adhesive agent after beinghardened. Further, since the activation temperature of the chelatingagent may well be not higher than the application temperature of theconductive adhesive agent, the required properties (especiallyactivation temperature) of the chelating agent come lenient, thusincreasing the number of the chelating agents that can be used.

In the above-mentioned invention, the following materials can be used.

As the binder resin, almost all resins relatively easily available canbe used. For example, as the thermo-hardening resin can be used epoxyresin, phenol resin, urea resin, melamine resin, furan resin,unsaturated-resin polyester resin, di-allyl phthalate resin, siliconresin, or the like. Also, as the thermo-hardening resin can be usedvinyl chloride resin, vinylidene chloride resin, polystyrene resin,ionomer, methyl-penten resin, poly-allomer, fluorine resin, apoly-imide, poly-amide, poly-amide-imide, poly-carbonate, modifiedpoly-phenylene oxide, poly-phenylene sulfide.

The micro-capsule may be made of such relatively easily availablethermo-hardening resins as vinyl chloride resin, vinylidene chlorideresin, polystyrene resin, ionomer, methyl-pentene resin, poly-allomer,fluorine resin, poly-amide, poly-imide, poly-amide-imide,poly-carbonate, modified poly-phenylene oxide, poly-phenylene sulfide,or the like. Note here that the melting temperature of the micro-capsulecan be adjusted arbitrarily by adjusting the molar weight of the resinor the film thickness of the micro-capsule.

If the above-mentioned variety of requirements of the conductiveadhesive agent and the packaging structure set by the invention are notsatisfied, no object of the invention can be realized. The reason isdescribed as follows.

If the melting point of the micro-capsule is not higher than theapplication temperature of the conductive adhesive agent, themicro-capsule melts before hardening, so that the elution preventingfilm-forming agent is released, thus forming an elution preventing filmon the conductive particle surfaces, thus increasing the connectionresistance of the packaging structure after hardening.

If the melting point of the micro-capsule is higher than the hardeningtemperature, the elution preventing film-forming agent does not reactwith the conductive particle even after hardening to thereby form noelution preventing film, thus failing to obtain the ion migrationresistance nor the sulfurization resistance.

Also, if as the elution preventing film-forming agent added to theconductive adhesive agent is employed such an agent that has as its maincomponent a chelating agent having an activation temperature higher thanthe hardening temperature (for example, bismthyol II having a meltingpoint of 246° C. as against a hardening temperature of 150° C.), theelution preventing film-forming agent does not react with the conductiveparticle even after hardening to thereby form no elution preventingfilm, thus failing to obtain the ion migration resistance nor thesulfurization resistance.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other objects of the invention will be more apparent fromthe following description taken in conjunction with the accompanyingdrawings and described in the accompanying claim. Many advantages of theinvention not described in the specification may be apparent to thoseskilled in the art.

FIG. 1 are expanded diagrams for showing an important part of aconductive adhesive agent according to a first embodiment of theinvention, of which FIG. 1 shows a state before hardening, FIG. 1B showsa state where continuity appears during hardening, and FIG. 1C shows astate after hardening;

FIG. 2 is a cross-sectional view for showing a flip chip packagingstructure according to a second embodiment of the invention;

FIG. 3 is a plan view for showing the chip element packaging structureaccording to a third embodiment of the invention;

FIG. 4 is a plan view for showing a printed-circuit board used inevaluation of ion migration resistance; and

FIG. 5 is a plan view for showing a testing sample used in evaluation ofsulfurization resistance.

DETAILED DESCRIPTION OF THE INVENTION

The following will describe embodiments of the invention with referenceto the drawings.

First Preferred Embodiment

This embodiment implements the invention in a conductive adhesive agent.FIGS. 1A-1C are expanded diagrams for showing an important part of theconductive adhesive agent according to this embodiment. FIG. 1A shows astate before being hardened, FIG. 1B shows a state where continuityappeared during its hardening, and FIG. 1C shows a state where it ishardened completely. In FIG. 1A, the conductive adhesive agent 1comprises a liquid-state binder resin 2 in which are mixed and disperseda conductive particle 3 and an elution preventing film-forming agent 4having a chelating agent as its main component. In a hardening stepshown in FIG. 1B, the conductive particles 3 are in contact with eachother and the elution preventing film-forming agent particles are stilldispersed in the binder resin 2 which is half-hardened. In FIG. 1C, theconductive particles 3 are in contact with each other with portionsthereof not in contact mutually being coated with an elution preventingfilm 5 having a metallic complex as its main component in the binderresin 2 which is half-hardened.

As the binder resin 2 the following may be used. That is, as thethermo-hardening resin may be used epoxy resin, phenol resin, urearesin, melanin resin, furan resin, unsaturated-resin polyester resin,diallyl phthalate resin, silicon resin, or the like. Also, as thethermo-plastic resin may be used vinyl chloride resin, vinylydenechloride resin, polystylene resin, ionomer, methyl-penten resin,poly-allomer, fluorine resin, poly-amide, poly-imide, poly-amide-imide,poly-carbonate, modified poly-phenylene oxide, poly-phenylene sulfide,or the like.

As the chelating agent constituting the main component of the elutionpreventing film-forming agent 4, for example, anthranilic acid (meltingpoint: 143° C.≈activation temperature) or pyrogallol (melting point:132° C.≈activation temperature) may be used if the conductive adhesiveagent has an application temperature of 25° C. and a hardeningtemperature of 150° C.

Also, as the conductive particle 3, Ag, an alloy of Cu, Cu—, or Ag or analloy of Cu, Ni, or Ag—Pd coated with Au or Ag may be used. Of these, Agis preferable taking into account the volume inherent resistance or thematerial cost.

Second Preferred Embodiment

This embodiment implements the invention in a flip-chip packagingstructure for a semiconductor device. As shown in FIG. 2, this packagingstructure comprises a printed-circuit board 6, which is one example ofthe electrical structure, and a semiconductor device 7, which is anotherexample of the electrical structure. The semiconductor device 7 iscomprised of an IC substrate 8 and a bump electrode 9 formed on thesurface of the IC substrate 8. The printed-circuit board 6 has an I/Oterminal electrode 10 on its surface. The I/O terminal electrode 10 hasformed thereon a conductive adhesive agent layer 1A made of theconductive adhesive agent 1 described in the first embodiment, throughwhich layer 1A are electrically interconnected the I/O terminalelectrode 10 and the bump electrode 9. Further, a sealing resin 11 isprovided to fill the gap between the semiconductor device 7 and theprinted-circuit board 6, thus constituting the flip-chip packagingstructure.

Third Preferred Embodiment

This embodiment implements the invention in a packaging structure for achip element. As shown in FIG. 3, this packaging structure has such aconfiguration that on the surface thereof are mounted an electrode 13 ofa printed-circuit board 12, which is one example of the electricalstructure, a chip resistor 14, which is another example of theelectrical structure, a chip coil 15, and a chip capacitor 16. Theelectrode 13 has formed thereon the conductive adhesive agent layer 1Amade of the conductive adhesive agent 1 described in the firstembodiment, through layer 1A are electrically interconnected theelectrode 13 and these chip elements 14, 15, and 16.

Examples of the above-mentioned embodiments are explained below.

First, practical examples (conductive adhesive agent) of the firstembodiment are described below.

PRACTICAL EXAMPLE 1

By this practical example, the conductive adhesive agent 1 described inthe first embodiment features the elution preventing film-forming agent4, which is a liquid agent which has as its main component ananthranilic acid (melting point: 143° C.≈activation temperature), whichis the chelating agent. The anthranilic acid reacts with an Ag particleto form an anthranilic acid Ag, which is a metallic complex, on theparticle surfaces. Note here that the activation temperature (reactiontemperature) of the anthranilic acid, the application temperature of theconductive adhesive agent, the hardening temperature of the conductiveadhesive agent satisfy the following relations:

 application temperature (32° C.) of conductive adhesiveagent<activation temperature (143° C.) of anthranilic acid;

and

activation temperature (143° C.) of anthranilic acid≦hardeningtemperature (150° C.) of binder resin.

Therefore, the elution preventing film-forming agent 4 containing theanthranilic acid reacts with the conductive particle 3 when the binderresin 2 is hardening, to form the elution preventing film 5 containingthe metallic complex. Also, the anthranilic acid Ag, which is a metalliccomplex formed by this reaction, may be assumed to be non-ionizing andinsoluble in water and an aqueous solution containing a hydrogen sulfideor sulfur oxide.

Next, a method of manufacturing the conductive adhesive agent accordingto this practical example is described as follow. The liquid binderresin 2 (7 weight-%) made of thermo-hardening epoxy resin, theconductive particle 3 (92 weight-%) made of Ag, the elution preventingfilm-forming agent 4 (2 weight-%) having anthranilic acid as its maincomponent, an addition agent, a dispersion agent, an adherence improver(2 weight-%), and the like are dispersed and mixed using a three-pieceroll to provide the conductive adhesive agent 1 of this practicalexample.

PRACTICAL EXAMPLE 2

As a feature of this practical example, in the configuration of theconductive adhesive agent described in practical example 1, the elutionpreventing film-forming agent is the elution preventing film-formingagent 4 which has, as its main component, 1-nitroso-2-naphthol (meltingpoint: 110° C.) which serves as the chelating agent employed in place ofanthranilic acid. The other conditions are totally the same as those ofpractical example 1, that is, the configuration conditions of theconductive adhesive agent material, the manufacturing method, theapplication temperature, the hardening temperature, or the like.

The 1-nitroso-2-naphthol has an activation temperature (reactiontemperature≈melting point) of (110° C. or so) and reacts with theconductive particle 3 when the binder resin 2 is being hardened, to forma metallic complex, that is, the elution preventing film 4 which has1-nitroso-2-naphthol Ag as its main component. The 1-nitroso-2-naphtholAg is an ionizing material and very easily solved in water and easilyabsorbs water and an aqueous solution which contains hydrogen sulfide orsulfur oxide.

PRACTICAL EXAMPLE 3

As a feature of this practical example, in the configuration of theconductive adhesive agent described in practical example 1, the elutionpreventing film-forming agent 4 is given as something obtained byencapsulating a chemical agent having anthranilic acid as its maincomponent in a micro-capsule with hexamethylene phthalamide resin(melting temperature: 87° C.). The other conditions are totally the sameas those of practical example 1, that is, the configuration conditionsof the conductive adhesive agent material, the manufacturing method, theapplication temperature, the hardening temperature, or the like. Thesoftening temperature of the micro-capsule, the application temperatureof the conductive adhesive agent, and the hardening temperature of theconductive adhesive agent satisfy the following relations:

application temperature of conductive adhesive agent (32° C.)<meltingtemperature of micro-capsule (87° C.);

melting temperature of micro-capsule (87° C.)≦hardening temperature ofbinder resin (150° C.);

and

 activation temperature of anthranilic acid (143° C.)≦hardeningtemperature of binder resin (150° C.).

Therefore, when the binder resin 2 is being hardened, the micro-capsulemelts to release the elution preventing film-forming agent 4 fromitself, which agent 4 (=anthranilic acid) in turn reacts with theconductive particle 3 to form the elution preventing film 5 containing ametallic complex.

Note here that the elution preventing film-forming agent 4 isencapsulated in the micro-capsule by a publicly known interfacepolymerization reaction method. The manufacturing method is detailed asfollows. Into an aqueous solution of 7.5 ml in which 0.4M of1,6-hexamethylene di-amine and 0.45M of sodium carbonate are solved isadded an equivalent amount of water, so that a 15-ml volume of thissolvent is subsequently is added to a 75-ml volume of a mixture solutionof chloroform and cyclo-hexan (volume ration: 1:4) containing a 5% ofanthranilic acid, which is then well stirred and emulsified to providewater/oil type emulsion. After five minutes of emulsification, phthaloyldichloride is added to the emulsion while stirring it. This causes thecondensation polymerization reaction to occur between phthaloyldi-chloride and di-amine on the surface of a water droplet in theemulsion, to produce hexamethylene phthalamide. The above steps causesthe elution preventing film-forming agent 4 to be encapsulated in amicro-capsule.

PRACTICAL EXAMPLE 4

As a feature of this practical example, in the configuration of theconductive adhesive agent described in practical example 1, the elutionpreventing film-forming agent 4 is given as something that has, as itsmain component, bismthyol II (melting point: 246° C.≈activationtemperature) in place of anthranilic acid and also the method includes astep of re-heating at a temperature higher than the activationtemperature of the elution preventing film-forming agent 4 after theconductive adhesive agent 1 is hardened. The other conditions aretotally the same as those of practical example 1, that is, theconfiguration conditions of the conductive adhesive agent material, themanufacturing method, the application temperature, the hardeningtemperature, or the like. The activation temperature of the elutionpreventing film-forming agent (chelating agent), the hardeningtemperature of the conductive adhesive agent 1, and the re-heatingtemperature satisfy the following relations:

hardening temperature of binder resin (150° C.)≦activation temperatureof bismthyol II (246° C.);

and

activation temperature of bismthyol II (246° C.)<re-heating temperature(250° C.).

PRACTICAL EXAMPLE 5

As a feature of this practical example, in the configuration of theconductive adhesive agent described in practical example 4, as thechelating agent constituting the main component of the elutionpreventing film-forming agent 4, anthranilic acid (activationtemperature: 143° C.) is employed in place of bismthyol II and also thiselution preventing film-forming agent 4 is encapsulated in amicro-capsule with hexamethylene phthalamide resin (melting temperature:162° C.). The other conditions are totally the same as those ofpractical example 1, that is, the configuration conditions of theconductive adhesive agent material, the manufacturing method, theapplication temperature, the hardening temperature, or the like. Theactivation temperature (reaction temperature) of the elution preventingfilm-forming agent 4, the hardening temperature of the conductiveadhesive agent 1, the re-heating temperature, and the meltingtemperature of the capsule satisfy the following relations:

hardening temperature of binder resin (150° C.)<melting temperature ofmicro-capsule (162° C.);

melting temperature of micro-capsule (162° C.)<re-heating temperature(170° C.);

and

activation temperature of hexamethylene phthalamide (143° C.)<re-heatingtemperature (170° C.).

Therefore, the elution preventing film-forming agent 4 staysnon-reactive during the hardening step but reacts with the conductiveparticle at the re-heating step to form the elution preventing film 5containing a metallic complex.

Corresponding to the above-mentioned practical examples 1-5, theconductive adhesive agent is prepared according to the followingcomparison examples 1-3.

COMPARISON EXAMPLE 1

The conductive adhesive agent according to this comparison example hassuch a configuration that he elution preventing film-forming agent 4 isremoved from the configuration of a prior art conductive adhesive agent,that is, the conductive adhesive agent 1 of practical example 1, withthe content ratio of the conductive particle 3 being the same aspractical example 1. That is, this conductive adhesive agent 1 comprisesthe liquid binder 2 (6 weight-%) made of a thermo-hardening epoxy resin,the conductive particle 3 (92 weight-%) made of Ag, and addition agents(2 weight-%) such as a hardening agent, dispersion agent, or adherenceimprover, which are dispersed and mixed using a three-piece roll.

COMPARISON EXAMPLE 2

This conductive adhesive agent according to this comparison example hassuch a configuration that the conductive adhesive agent of practicalexample 1 contains, as the chelating agent, bismthyol II (melting point:246° C.≈activation temperature) having an activation temperature higherthan the hardening temperature of the conductive adhesive agent. Theactivation temperature of the chelating agent, the applicationtemperature of the conductive adhesive agent, and the hardeningtemperature of the conductive adhesive agent satisfy the followingconditions:

application temperature of the conductive adhesive agent (32°C.)<hardening temperature of binder resin (150° C.);

and

hardening temperature of binder resin (150° C.)<activation temperatureof bismthyol II (246° C.).

Therefore, in this comparison example 2, the chelating agent staysnon-reactive at the hardening step for the binder resin, so that theelution preventing film 5 containing a metallic complex is not formed onthe surfaces of the conductive particle 3.

COMPARISON EXAMPLE 3

This conductive adhesive agent has such a configuration that theconductive adhesive agent of practical example 1 contains, as thechelating agent, toluene-3,4-dithiol (melting point: 31° C.≈activationtemperature) which has an activation temperature lower than theapplication temperature of the binder resin 2. The activationtemperature of the chelating agent, the application temperature of theconductive adhesive agent, and the hardening temperature of theconductive adhesive agent satisfy the following conditions:

activation temperature of toluene-3,4-dithiol (31° C.)<applicationtemperature of conductive adhesive agent (32° C.);

and

 application temperature of conductive adhesive agent (32° C)<hardeningtemperature of binder agent (150° C.).

Therefore, the chelating agent in an unhardened state reacts with theconductive particle to form an elution preventing film containing ametallic complex on the particle surfaces.

The conductive adhesive agent thus prepared according to practicalexamples 1-5 and comparison examples 1-3 is used to form a conductiveadhesive agent layer for evaluation and measurement as follows.

Evaluation of Ion Migration Resistance (Water Droplet Drop Test)

A water droplet drop test is a method for evaluating the ion migrationresistance of a material rapidly and simply. The testing method isdetailed as follows. As shown in FIG. 4, as a testing sample,comb-shaped conductive adhesive agent layers 18 and 19 are formed on aceramic-made testing substrate 17 by a screen printing method. Theconductive adhesive agent layers 18 and 19 are separated from each otherby a predetermined inter-electrode distance (400 μm) and arranged asopposed so that their tips may alternate, with no current generallyflowing therebetween.

Deionized water is dropped on thus formed conductive adhesive agentlayers 18 and 19 and a DC voltage (1 V) is applied therebetween. Then, atime lapse is measured which elapses from a time point ofshort-circuiting between the conductive adhesive agent layers 18 and 19up to a time point that a current starts to flow, so that the ionmigration resistance is measured on the basis of that short-circuitingtime lapse.

Evaluation of Sulfurization Resistance

As shown in FIG. 5, on a glass epoxy-made testing board 20, agold-plated electrode 21 is formed, on which is in turn formed aconductive adhesive agent layer 1A made of the conductive adhesive agent1 by the screen printing method. On the conductive adhesive agent layer1A is then mounted a 3216-size 0-Ω resistor (terminal plating: SnPbsolder) 22 using a mount packaging machine. Next, to harden theconductive adhesive agent layer 1A, it is heated in an oven at 150° C.for 30 minutes. Thus prepared samples are measured for the initialconnection resistance and then left in an enclosed bath filled withhydrogen sulfide to thereby measure a change in the connectionresistance, thus evaluating the sulfurization resistance. The testingconditions includes a temperature of 40° C., a humidity of 90%, aconcentration of the hydrogen sulfide of 3 ppm, and a testing time of 96hours.

The results of the above-mentioned evaluation and measurements aresummarized in Table 1. Note here that the conductive adhesive agent wasapplied in all the tests at an application temperature (workingtemperature) of 32° C.

TABLE 1 Chelating Sulfurization agent Capsule Metallic Migration testresults (Activation (Softening complex Re- Test Initial value −>temperature) temperature) Solubility heating results value after 96 HEmbodiment Anthranilic None Insoluble None 965 sec 42 mΩ −> 42 mΩ 1 acid(143° C.) Embodiment 1-nitroso- None Soluble None 842 sec 42 mΩ −> 45 mΩ2 2-naphthaol (110° C.) Embodiment Anthranilic HMFA Insoluble None 970sec 38 mΩ −> 38 mΩ 3 acid (87° C.) (143° C.) Embodiment Bismthyol NoneInsoluble 250° C. 960 sec 35 mΩ −> 35 mΩ 4 II 5 min (246° C.) EmbodimentAnthranilic HMFA Insoluble 170° C. 963 sec 35 mΩ −> 35 mΩ 5 acid (162°C.) 5 min (143° C.) Comparison None None — None  86 sec 35 mΩ −> 98 mΩexample 1 Comparison Toluene- None Insoluble None 964 sec 126 mΩ −> 126mΩ example 2 3,4-dithiol (31° C.) Comparison Bismthyol None InsolubleNone  86 sec  36 mΩ −> 101 mΩ example 3 II (246° C.) *HMFA:Hexamethylene phthalamide

Comparison of the conductive adhesive agents according to practicalexamples 1-5 to comparison examples 1-3 shows the following. That is,the evaluation of the ion migration resistance indicates that the timelapse up to a point in time when a current starts to flow was prolongedas compared to the case of using the prior art conductive adhesive agent(comparison example 1) so it is confirmed that the ion migrationresistance was improved. Also, the evaluation of the sulfurizationindicates that a ratio of a change in the connection resistance asmeasured before and after testing was reduced as compared to comparisonexample 1 so it is confirmed that the sulfurization resistance wasimproved.

Further, the comparison assures the following. That is, comparisonbetween practical example 1 where the metallic complex constituting themain component of the elution preventing film 5 formed on the surfacesof the conductive particle 3 is insoluble in water and an aqueoussolution containing hydrogen sulfide or sulfur oxide and practicalexample 2 where it is soluble them reveals that practical example 1 cameup with better ion migration resistance and sulfurization resistance.This is considered because the elution preventing film (metalliccomplex) formed, if it is insoluble in water and an aqueous solutioncontaining hydrogen sulfide or sulfur oxide, is less subject toflake-off even when the water or the aqueous solution containing sulfuris condensed on the surfaces of the film.

Comparison between practical example 1 where the elution preventingfilm-forming agent 4 (chelating agent) is added as it is into theconductive adhesive agent 1 and practical example 3 where it is added asencapsulated in a micro-capsule reveals that practical example 3 came upwith a lower initial connection resistance. This is considered becausewhen it is encapsulated in the micro-capsule, the reaction of theelution preventing film-forming agent 4 as unhardened can be more surelyinhibited, thus reducing the amount of the insulating elution preventingfilm 5 (metallic complex) which exists at a contact point between theconductive particles 3 or the conductive particle 3 and the electrode 13or 21. Note here that although in practical example 3 the elutionpreventing film-forming agent 4 which has, as its main component,anthranilic acid having an activation temperature higher than theapplication temperature of the conductive adhesive agent 1 isencapsulated in a micro-capsule, the elution preventing film-formingagent 4 can have, as its main component, such a chelating agent that hasan activation temperature lower than the application temperature of theconductive adhesive agent 1, thus extending the range of selectableelution preventing film-forming agents (chelating agents) as compared topractical example 1.

Comparison between practical example 1 using the elution preventingfilm-forming agent 4 having as its main component such a chelating agentthat becomes reactive at a hardening step of the conductive adhesiveagent 1 and practical example 4 using the elution preventingfilm-forming agent 4 having as its main component such a chelating agentthat does not become reactive at the hardening step so that the elutionpreventing film-forming agent 4 may become reactive at the re-heatingstep after the hardening step reveals that practical example 4 came upwith a lower initial connection resistance, almost equal to an initialvalue obtained in the case (comparison example 1) where the prior artconductive adhesive agent was used. This is considered because that inpractical example 4 the elution preventing film 4 becomes reactive information after continuity appeared at the hardening step, so that theelution preventing film 5 is formed little at a continuity site.

As may be clear from practical example 5, when the elution preventingfilm-forming agent 4 is encapsulated in a micro-capsule in practicalexample 4, almost the same ion migration resistance and sulfurizationresistance can be obtained and, in addition to that, the range ofselectable elution preventing film-forming agent 4 is extended. This isbecause practical example 4 needs to use the elution preventingfilm-forming agent 4 containing such a chelating agent that has anactivation temperature (reaction temperature) higher than the hardeningtemperature, whereas practical example 5 can accept any activationtemperature of the elution preventing film-forming agent 4 as far as themelting temperature of the micro-capsule is set higher than thehardening temperature of the binder resin 2. For example, it is possibleto use even such an elution preventing film-forming agent 4 that has anactivation temperature lower than the application temperature of theconductive adhesive agent 1.

Note here that if the conditions described in practical examples 1-5 arenot satisfied, the intended effects cannot be obtained. The evidence isgiven in comparison examples 2 and 3.

Comparison example 2 indicates a case of using such an elutionpreventing film-forming agent 4 that has, as its main component, achelating agent having an activation temperature lower than theapplication temperature of the conductive adhesive agent 1. This casecame up with an extremely high initial connection resistance as comparedto practical example 1, that is, a case where the activation temperatureis higher than the application temperature. This is because that theelution preventing film-forming agent 4 reacts as unhardened with theconductive particle 3 to form the elution preventing film 5 (metalliccomplex), so that an insulating elution preventing film 5 (metalliccomplex) is present at a site related to continuity of the conductiveparticles 3, thus increasing the contact resistance.

Also, comparison example 3 indicates a case of using such an elutionpreventing film-forming agent 4 that has, as its main component, achelating agent having an activation temperature higher than thehardening temperature of the conductive adhesive agent 1. Comparisonexample 3 came up with such a result that the ion migration resistanceand the sulfurization resistance were extremely inferior as compared topractical example 1, that is, a case where the activation temperature ofthe chelating agent is lower than the hardening temperature. This isbecause that the elution preventing film-forming agent 4 is not reactiveat the hardening step for the conductive adhesive agent 1 (binder resin2), thus failing to form the elution preventing film (metallic complex)4 on the surfaces of the conductive particle 3.

Next, the practical examples of the second preferred embodiment (flipchip packaging structure for semiconductor device) are described asfollows.

PRACTICAL EXAMPLE 6

As a feature of this practical example, as the elution preventingfilm-forming agent 4, the conductive adhesive agent of practical example1 using, as its man component, anthranilic acid, which is a chelatingagent (except that a thermoplastic epoxy resin is used as the liquidbinder resin 2), is used to flip-chip package the semiconductor device 7on the printed-circuit board 6. That is, the conductive adhesive agent 1described in practical example 1 is transferred by a publicly knownmethod onto the bump electrode 9 of the semiconductor device 7. Then,with thus transferred conductive adhesive agent 1 as aligned with theI/O terminal electrode 10 of the printed-circuit board 6, thesemiconductor device 7 is flip-chip packaged on the printed-circuitboard 6. Then, after the conductive adhesive agent 1 is hardened, anelectrical test is performed to then harden the sealing resin 11 made ofthermo-hardening epoxy resin supplied between the printed-circuit board6 and the semiconductor device 7 which came up with good results oftesting, to thereby seal the related jointed site, thus providing a flipchip packaging structure.

PRACTICAL EXAMPLE 7

As a feature of this practical example, as the elution preventingfilm-forming agent 4, the conductive adhesive agent 1 of practicalexample 2 having, as its main component, 1-nitroso-2-naphthol, which isa chelating agent, is used to constitute the flip chip packagingstructure. The configuration and the manufacturing method of the flipchip packaging structure are totally the same as those of practicalexample 6 except the conductive adhesive agent employed.

PRACTICAL EXAMPLE 8

As a feature of this practical example, as the elution preventingfilm-forming agent 4, such a material that has, as its main component,anthranilic acid, which is a chelating agent, is used and, at the sametime, the conductive adhesive agent 1 of practical example 3 forencapsulating this elution preventing film-forming agent 4 in amicro-capsule with a hexamethylene phtalamide resin is used toconstitute the flip chip packaging structure. The configuration and themanufacturing method of the flip chip packaging structure are totallythe same as those of practical example 6 except the conductive adhesiveagent 1 employed.

PRACTICAL EXAMPLE 9

As a feature of this practical example, as the elution preventingfilm-forming agent 4, the conductive adhesive agent 1 having, as itsmain component, the bismthyol II, which is a chelating agent, ishardened and then undergoes re-heating according to the method ofpractical example 4, to constitute the flip chip packaging structure.The configuration and the manufacturing method of the flip chippackaging structure are totally the same as those of practical example 6except the conductive adhesive agent employed.

PRACTICAL EXAMPLE 10

As a feature of this practical example, as the elution preventingfilm-forming agent 4, such a material that has, as its main component,anthranilic acid, which is a chelating agent, and also that encapsulatesthis elution preventing film-forming agent 4 in a micro-capsule with ahexamethylene phtalamide resin is used and then undergoes re-heatingafter the conductive adhesive agent 1 is hardened according to themethod of practical example 5, to form the flip chip packagingstructure. The configuration and the manufacturing method of the flipchip packaging structure are totally the same as those of practicalexample 6 except the conductive adhesive agent 1 employed.

COMPARISON EXAMPLES 4-6

Corresponding to the above-mentioned practical examples 6-10, the flipchip packaging structures of comparison examples 4-6 are prepared.

These flip chip packaging structures are supposed to use the conductiveadhesive agent of comparison example 1 and also have the same packagingconstructions as those of practical examples 6-10.

Thus prepared flip chip packaging structures of practical examples 6-10and comparison examples 4-6 are evaluated in terms of reliabilityaccording to the following method.

That is, as flowing an in-actual-use current (10 mA) through these flipchip packaging structures, the method measured them for a change in theconnection resistance in a hot and humid environment (temperature: 85°C., humidity: 85%, testing time 1000 hours), to perform evaluation andmeasurement of the ion migration resistance. Likewise, as flowing anin-actual-use current (10 mA) through them, the method measured them fora change in the connection resistance in a hydrogen sulfide atmosphere(temperature: 40° C., humidity: 90%, concentration of hydrogen sulfide:3 ppm, testing time: 96 hours), to perform evaluation and measurement ofthe sulfurization resistance. The results are shown in Table 2.

TABLE 2 Migration Sulfurization Chelating results test results agentCapsule Metallic Initial value Initial value (Activation (Softeningcomplex Re- −> value after −> value temperature) temperature) Solubilityheating 1000 H after 96 H Embodiment Anthranilic None Insoluble None 21mΩ −> 21 mΩ 21 mΩ −> 21 mΩ  6 acid (143° C.) Embodiment 1-nitroso- NoneSoluble None 21 mΩ −> 27 mΩ 21 mΩ −> 23 mΩ  7 2-naphthaol (110° C.)Embodiment Anthranilic HMFA Insoluble None 19 mΩ −> 19 mΩ 19 mΩ −> 19 mΩ 8 acid (87° C.) (143° C.) Embodiment Bismthyol None Insoluble 250° C.17 mΩ −> 17 mΩ 17 mΩ −> 17 mΩ  9 II 5 min (246° C.) EmbodimentAnthranilic HMFA Insoluble 170° C. 17 mΩ −> 17 mΩ 17 mΩ −> 17 mΩ 10 acid(162° C.) 5 min (143° C.) Comparison None None — None 17 mΩ −> OPEN  17mΩ −> 50 mΩ example 4 Comparison Toluene- None Insoluble None 1.5 Ω −>1.5 Ω 1.5 Ω −> 1.5 Ω example 5 3,4-dithiol (31° C.) Comparison BismthyolNone Insoluble None 1.8 mΩ −> 121    18 mΩ −> 53 mΩ example 6 II mΩ(246° C.) *HMFA: Hexamethylene phthalamide

Comparison of the flip chip packaging structures according to practicalexamples 6-10 to comparison examples 4-6 shows the following. That is,the evaluation of the ion migration resistance indicates that the timelapse up to a point in time when a current starts to flow was prolongedas compared to the case of using the prior art conductive adhesive agent(comparison example 4) so it is confirmed that the ion migrationresistance was improved. Also, the evaluation of the sulfurizationindicates that a ratio of a change in the connection resistance asmeasured before and after testing was reduced as compared to comparisonexample 4 so it is confirmed that the sulfurization resistance wasimproved.

Further, the comparison assures the following. That is, comparisonbetween practical example 6 where the elution preventing film 5 formedon the surfaces of the conductive particle 3 is insoluble in water andan aqueous solution containing hydrogen sulfide or sulfur oxide andcomparison example 7 where it is soluble in them reveals that practicalexample 6 came up with better ion migration resistance and sulfurizationresistance. This is considered because the elution preventing film 5formed, if it is insoluble in water and an aqueous solution containinghydrogen sulfide or sulfur oxide, is less subject to flake-off even whenthe water or the aqueous solution containing sulfur is condensed on thesurfaces of the film.

Also, comparison between practical example 6 where the elutionpreventing film-forming agent 4 is added as it is into the conductiveadhesive agent 1 and practical example 8 where it is added asencapsulated in a micro-capsule reveals that practical example 8 came upwith a lower initial connection resistance. This is considered becausewhen it is encapsulated in the micro-capsule, the reaction of theelution preventing film-forming agent 4 as unhardened can be more surelyinhibited, thus reducing the amount of the insulating elution preventingfilm 5 which exists at a contact point between the conductive particles3 or the conductive particle 3 and the electrode 13 or 21. Note herethat in practical example 8 the elution preventing film-forming agent 4which has, as its main component, anthranilic acid having a reactiontemperature (activation temperature) higher than the applicationtemperature of the conductive adhesive agent 1 is encapsulated in amicro-capsule. In this practical example 8, however, it is possible touse even such an elution preventing film-forming agent 4 that has, asits main component, a chelating agent exhibiting a reaction temperature(activation temperature) lower than the application temperature of theconductive adhesive agent 1, thus extending the range of selectableelution preventing film-forming agents (chelating agents) as compared topractical example 6.

Further, comparison between practical example 6 using the elutionpreventing film-forming agent 4 which becomes reactive at the hardeningstep of the conductive adhesive agent 1 and practical example 9 usingthe elution preventing film-forming agent 4 which is not reactive atthat hardening step so that reaction may occur at the re-heating stepreveals that practical example 9 came up with a lower initial connectionresistance, almost equal to an initial value obtained in the case(comparison example 1) where the prior art conductive adhesive agent wasused. This is considered because that in practical example 9 the elutionpreventing film 4 becomes reactive after continuity appeared at thehardening step, so that the elution preventing film 5 is formed littleat a continuity site.

Also, as may be clear from practical example 10, when the elutionpreventing film-forming agent 4 is encapsulated in a micro-capsule inthe configuration of practical example 9, almost the same ion migrationresistance and sulfurization resistance can be obtained and, in additionto that, the range of selectable elution preventing film-forming agent 4is extended. This is because practical example 9 needs to use theelution preventing film-forming agent 4 exhibiting an activationtemperature higher than the hardening temperature, whereas practicalexample 10 can accept any reaction temperature (activation temperature)of the elution preventing film-forming agent 4 as far as the meltingtemperature of the micro-capsule is set higher than the hardeningtemperature of the binder resin 2. Although such an elution preventingfilm-forming agent 4 that has, as its main component, anthranilic acidhaving an activation temperature higher than the application temperatureof the conductive adhesive agent 1 has been used in practical example10, this practical example 10 can use such an agent 4 that has, as itsmain component, a chelating agent exhibiting an activation temperaturelower than the application temperature of the conductive adhesive agent1.

Note here that if the conditions described in practical examples 6-10are not satisfied, the intended effects cannot be obtained. The evidenceis given in comparison examples 5 and 6.

Comparison example 5 indicates a case of using such an elutionpreventing film-forming agent 4 that has, as its main component, achelating agent having an activation temperature lower than theapplication temperature of the conductive adhesive agent 1. This casecame up with an extremely high initial connection resistance as comparedto practical example 6, that is, a case where the reaction temperature(activation temperature) of the elution preventing film is higher thanthe application temperature of the conductive adhesive agent 1. This isbecause that the elution preventing film-forming agent 4 reacts asunhardened with the conductive particle 3 to form an elution preventingfilm (metallic complex), so that an insulating elution preventing film(metallic complex) is present at a site related to continuity of theconductive particles 3, thus increasing the contact resistance.

Also, comparison example 6 indicates a case where the elution preventingfilm-forming agent 4 has a reaction temperature (activation temperature)higher than the hardening temperature of the conductive adhesive agent1. This case came up with such a result that the ion migrationresistance and the sulfurization resistance were extremely inferior ascompared to practical example 5, that is, a case where the reactiontemperature (activation temperature) of the elution preventingfilm-forming agent 4 is lower than the hardening temperature of theconductive adhesive agent 1. This is because that the elution preventingfilm-forming agent 4 is not reactive at the hardening step for theconductive adhesive agent 1 (binder resin 2), thus failing to form theelution preventing film 5 on the surfaces of the conductive particle 3.

Thus, practical examples 6-10 (flip chip packaging structure) alsoprovide almost the same effects as those by practical examples 1-5(conductive adhesive agent).

Although practical examples 6-10 have used the conductive adhesive agent1 having a thermoplastic epoxy resin to provide electric connectionbetween the semiconductor device and the printed-circuit board, athermo-hardening epoxy resin may be used instead to have almost the sameeffects like in the case of the first embodiment.

The following will describe the practical examples of the thirdembodiment (chip-element packaging structure).

PRACTICAL EXAMPLE 11

This practical example provides a chip-element packaging structure whichis made using a conductive adhesive agent of practical example 1. Notehere that practical example 1 has used such an elution preventingfilm-forming agent 4 that has, as its main component, an anthranilicacid, which is an chelating agent. This chip-element packaging structurecomprises a printed-circuit board (30×60 mm, thickness: 1.6 mm) 12 madeof glass epoxy, on which the electrode 13 is formed by Au plating andthen the 0-Ω chip resistor (3216 size, SnPb plating) 14, the chip coil(diameter: 8 mmφ, height: 4 mm) 15, and the chip capacitor (3215 size,SnPb plating) 16 are packaged.

This chip-element packaging structure is made as follows. First, theconductive adhesive agent 1 is screen-printed on the electrode 13 of theprinted-circuit board 12. Then, the chip elements 14, 15, and 16 aremounted on the electrode 13 using an existing element mounting machineand undergo heating in an oven at 150° C. for 30 minutes, thus hardeningthe conductive adhesive agent 1.

PRACTICAL EXAMPLE 12

As a feature of this practical example, the chip-element packagingstructure is made up of the conductive adhesive agent 1 of practicalexample 2 using such an elution preventing film-forming agent 4 thathas, as its main component, 1-nitroso-2-naphthol, which is a chelatingagent. The configuration and the manufacturing method of thechip-element packaging structure are totally the same as those ofpractical example 11 except the conductive adhesive agent employed.

PRACTICAL EXAMPLE 13

As a feature of this practical example, as the elution preventingfilm-forming agent 4, the conductive adhesive agent, which is achelating agent, is used and, the conductive adhesive agent of practicalexample 3 for encapsulation into a micro-capsule by use of hexamethylenephtalamide is used to make the chip-element packaging structure. Theconfiguration and the manufacturing method of the chip-element packagingstructure are totally the same as those of practical example 11 exceptthe conductive adhesive agent 1 employed.

PRACTICAL EXAMPLE 14

As a feature of this practical example, as the elution preventingfilm-forming agent 4, the conductive adhesive agent 1 having, as itsmain component, the bismthyol II, which is a chelating agent, is usedand then undergoes re-heating after the conductive adhesive agent ishardened according to the method of practical example 3, to constitutethe chip-element packaging structure. The configuration and themanufacturing method of the chip-element packaging structure are totallythe same as those of practical example 11 except the conductive adhesiveagent 1 employed.

PRACTICAL EXAMPLE 15

As a feature of this practical example, as the elution preventingfilm-forming agent 4, such a material that has, as its main component,anthranilic acid, which is a chelating agent, and also that encapsulatesthis elution preventing film-forming agent 4 in a micro-capsule with ahexamethylene phtalamide resin is used and then undergoes re-heatingafter the conductive adhesive agent 1 is hardened according to themethod of practical example 5, to form the flip chip packagingstructure. The configuration and the manufacturing method of the flipchip packaging structure are totally the same as those of practicalexample 11 except the conductive adhesive agent 1 employed.

COMPARISON EXAMPLES 7-9

Corresponding to the above-mentioned practical examples 11-15, thechip-element packaging structures of comparison examples 7-9 areprepared.

These chip-element packaging structures are supposed to use theconductive adhesive agent of comparison example 1 and also have the samepackaging constructions as those of practical examples 11-15.

Thus prepared chip-element packaging structures of practical examples11-15 and comparison examples 7-9 are evaluated in terms of reliabilityaccording to the following method.

As flowing an in-actual-use current (10 mA) through these chip-elementpackaging structures, the method measured them for a change in theconnection resistance in a hot and humid environment (temperature: 85°C., humidity: 85%, testing time 10000 hours), to perform evaluation andmeasurement of the ion migration resistance. Likewise, as flowing anin-actual-use current (10 mA) through them, the method measured them fora change in the connection resistance in a hydrogen sulfide atmosphere(temperature: 40° C., humidity: 90%, concentration of hydrogen sulfide:3 ppm, testing time: 96 hours), to perform evaluation and measurement ofthe sulfurization resistance. The results are shown in Table 3.

TABLE 3 Migration Sulfurization Chelating results test results agentCapsule Metallic Initial value Initial value (Activation (Softeningcomplex Re- −> value after −> value temperature) temperature) Solubilityheating 1000 H after 96 H Embodiment Anthranilic None Insoluble None 30mΩ −> 30 mΩ 30 mΩ −> 30 mΩ 11 acid (143° C.) Embodiment 1-nitroso- NoneSoluble None 31 mΩ −> 35 mΩ 31 mΩ −> 38 mΩ 12 2-naphthaol (110° C.)Embodiment Anthranilic HMFA Insoluble None 27 mΩ −> 27 mΩ 27 mΩ −> 27 mΩ13 acid (87° C.) (143° C.) Embodiment Bismthyol None Insoluble 250° C.24 mΩ −> 24 mΩ 24 mΩ −> 24 mΩ 14 II 5 min (246° C.) EmbodimentAnthranilic HMFA Insoluble 170° C. 24 mΩ −> 24 mΩ 24 mΩ −> 24 mΩ 15 acid(162° C.) 5 min (143° C.) Comparison None None — None 24 mΩ −> OPEN 24mΩ −> 59 mΩ example 7 Comparison Toluene- None Insoluble None 2.7 Ω −>2.7 Ω 2.7 Ω −> 2.7 Ω example 8 3,4-dithiol (31° C.) Comparison BismthyolNone Insoluble None 25 mΩ −> 163    25 mΩ −> 67 mΩ example 9 II mΩ (246°C.) *HMFA: Hexamethylene phthalamide

Comparison of the chip-element packaging structures according topractical examples 11-15 to comparison examples 7-9 shows the following.That is, the evaluation of the ion migration resistance indicates thatthe time lapse up to a point in time when a current starts to flow wasprolonged as compared to the case of using the prior art conductiveadhesive agent (comparison example 7) so it is confirmed that the ionmigration resistance was improved. Also, the evaluation of thesulfurization indicates that a ratio of a change in the connectionresistance as measured before and after testing was reduced as comparedto comparison example 7 so it is confirmed that the sulfurizationresistance was improved.

Further, the comparison assures the following. That is, comparisonbetween practical example 11 where the metallic complex formed on thesurfaces of the conductive particle is insoluble in water and an aqueoussolution containing hydrogen sulfide or sulfur oxide and comparisonexample 12 where it is soluble in them reveals that practical example 11came up with better ion migration resistance and sulfurizationresistance. This is considered because the elution preventing film 5formed, if it is insoluble in water and an aqueous solution containinghydrogen sulfide or sulfur oxide, is less subject to flake-off even whenthe water or the aqueous solution containing sulfur is condensed on thesurfaces of the film.

Also, comparison between practical example 11 where the elutionpreventing film-forming agent 4 is added as it is into the conductiveadhesive agent 1 and practical example 13 where it is added asencapsulated in a micro-capsule reveals that practical example 13 cameup with a lower initial connection resistance. This is consideredbecause when it is encapsulated in the micro-capsule, the reaction ofthe elution preventing film-forming agent 4 as unhardened can be moresurely inhibited, thus reducing the amount of the insulating elutionpreventing film (metallic complex) which exists at a contact pointbetween the conductive particles 3 or the conductive particle 3 and theelectrode 21. Note here that although practical example 13 has shown thecase where the elution preventing film-forming agent 4 which has, as itsmain component, anthranilic acid, which is a chelating agent having anactivation temperature higher than the application temperature of theconductive adhesive agent 1, is encapsulated in a micro-capsule, it ispossible to use even such an elution preventing film-forming agent 4that has, as its main component, a chelating agent exhibiting anactivation temperature lower than the application temperature of theconductive adhesive agent 1, thus extending the range of selectableelution preventing film-forming agents 4 (chelating agents) as comparedto practical example 11.

Further, comparison between practical example 13 using the elutionpreventing film-forming agent 4 which becomes reactive at the hardeningstep of the conductive adhesive agent 1 and practical example 14 usingthe elution preventing film-forming agent 4 which is not reactive atthat hardening step so that reaction may occur at the re-heating stepreveals that practical example 14 came up with a lower initialconnection resistance, almost equal to an initial value obtained in thecase (comparison example 7) where the prior art conductive adhesiveagent was used. This is considered because that in practical example 14the elution preventing film 4 becomes reactive after continuity appearedat the hardening step, so that the elution preventing film 5 is formedlittle at a continuity site.

Also, as may be clear from practical example 15, when the elutionpreventing film-forming agent 4 is encapsulated in a micro-capsule inthe configuration of practical example 14, almost the same ion migrationresistance and sulfurization resistance can be obtained and, in additionto that, the range of selectable elution preventing film-forming agent 4(chelating agent) is extended. This is because practical example 14needs to use the elution preventing film-forming agent 4 which has, asits main component, a chelating agent exhibiting an activationtemperature higher than the hardening temperature, whereas practicalexample 15 can accept any activation temperature of the elutionpreventing film-forming agent 4 (chelating agent) as far as the meltingtemperature of the micro-capsule is set higher than the hardeningtemperature of the binder resin 2. Although such an elution preventingfilm-forming agent 4 that has, as its main component, anthranilic acidhaving an activation temperature higher than the application temperatureof the conductive adhesive agent 1 has been used in practical example15, this practical example can use such an agent 4 that has, as its maincomponent, a chelating agent exhibiting an activation temperature lowerthan the application temperature of the conductive adhesive agent 1.

Note here that if the conditions described in practical examples 11-15are not satisfied, the intended effects cannot be obtained. The evidenceis given in comparison examples 8 and 9.

Comparison example 8 indicates a case of using such an elutionpreventing film-forming agent 4 that a reaction temperature (activationtemperature) lower than the application temperature of the conductiveadhesive agent 1. This case came up with an extremely high initialconnection resistance as compared to practical example 11, that is, acase where the above-mentioned reaction temperature (activationtemperature) is higher than the application temperature of theconductive adhesive agent 1. This is because that the elution preventingfilm-forming agent 4 reacts as unhardened with the conductive particle 3to form the elution preventing film 5, so that an insulating elutionpreventing film 5 (metallic complex) is present at a site related tocontinuity of the conductive particles 3, thus increasing the contactresistance.

Also, comparison example 9 indicates a case where the elution preventingfilm-forming agent 4 has a reaction temperature (activation temperature)higher than the hardening temperature of the conductive adhesive agent1. This case came up with such a result that the ion migrationresistance and the sulfurization resistance were extremely inferior ascompared to practical example 11, that is, a case where the reactiontemperature (activation temperature) is lower than the hardeningtemperature of the binder resin 2. This is because that the elutionpreventing film-forming agent 4 is not reactive at the hardening step ofthe conductive adhesive agent 1, thus failing to form the elutionpreventing film 5 on the surfaces of the conductive particle 3.

Thus, practical examples 11-15 (chip-element packaging structure) alsoprovide almost the same effects as those by practical examples 1-5(conductive adhesive agent) and practical examples 6-10 (flip chippackaging structure).

Although practical examples 11-15 have shown only the packagingstructures for chip elements as an example of the packaging structurefor the elements, of course they can be used to package all the otherelements including, for example, such package elements as a QFP (QuadFlat Package), CSP (Chip Scale Package), or BGA (Ball Grid Array), suchchip or lead elements as an electrolytic capacitor, diode, or switch,and IC bare packages. Also, the elution preventing film-forming agentand the like are not limited in application to the above-mentionedembodiments as far as the requirements are satisfied.

In any of the above-mentioned practical examples, the elution preventingfilm-forming agent 4 can be added, as dispersed in a non-polar solvent,to a conductive adhesive agent. Then, the following will occur.

Since a non-polar solvent serves to inhibit the reaction of a chelatingagent, if the elution preventing film-forming agent 4 is added, asdispersed in the non-polar solvent, to a conductive adhesive agent, thechelating agent is little reactive in a state where the binder resin isnot hardened yet. Then, when the binder resin is being hardened, thechelating agent reacts with a conductive particle to form an elutionpreventing film containing a metallic complex. Accordingly, the elutionpreventing film 5 is formed further less when the binder resin is nothardened yet, thus surely inhibiting a rise in the connection resistancein the conductive adhesive agent 1 after hardening. Further, since theactivation temperature of the chelating agent may be lower than theapplication temperature of the conductive adhesive agent, the requiredproperties (especially, activation temperature) of the chelating agentbecome lenient, thus extending the range of selectable chelating agentsthat much.

As is clear from the above-mentioned embodiments and practical examples,by the invention such a packaging structure that is excellent in the ionmigration resistance and the sulfurization resistance as compared to aprior art one can be obtained.

Also, the invention, if applied to such a packaging structure as a flipchip or chip-element packaging structure, improves the insulationreliability to thereby enable reducing the connection distance such asan inter-electrode distance, thus saving on a space for the packagingstructure.

Further, since the invention improves the reliability againstsulfurization, it can be applied to such a product that may be used in agas atmosphere containing a lot of sulfur, such as in the neighboringarea of hot springs or in the vicinity of volcanoes, thus greatlypossibly extending the application fields.

Although the invention has been described with respect to its mostpreferred embodiments, their combination and the arrangement can bevariously changed without departing from the spirit and the scope of theaccompanying claims.

What is claimed is:
 1. A conductive adhesive agent comprising: a binderresin; a conductive particle; and an elution preventing film-formingagent, wherein said elution preventing film-forming agent becomesreactive after electric continuity through said conductive particleappeared in the conductive adhesive agent when said binder resin isbeing hardened, to thereby form an elution preventing film on a surfaceof said conductive particle, wherein said elution preventingfilm-forming agent is added, as dispersed in a non-polar solvent, to theconductive adhesive agent.
 2. The conductive adhesive agent according toclaim 1, wherein a reaction temperature of said elution preventingfilm-forming agent satisfies conditions of: application temperature ofconductive adhesive agent<reaction temperature of elution preventingfilm-forming agent; and reaction temperature of elution preventingfilm-forming agent≦hardening temperature of binder resin.
 3. Theconductive adhesive agent according to claim 1, wherein said elutionpreventing film-forming agent contains a chelating agent, said chelatingagent becoming reactive after electric continuity through saidconductive particle appeared in the conductive adhesive agent when saidbinder resin is being hardened, to thereby form an elution preventingfilm containing a metallic complex on a surface of said conductiveparticle.
 4. The conductive adhesive agent according to claim 3, whereinan activation temperature of said chelating agent satisfies conditionsof:  application temperature of conductive adhesive agent<activationtemperature of chelating agent; and activation temperature of chelatingagent≦hardening temperature of binder resin.
 5. The conductive adhesiveagent according to claim 4, wherein said elution preventing film-formingagent is encapsulated in a micro-capsule, a melting temperature of saidmicro-capsule and an activation temperature of a chelating agentcontained in said elution preventing film-forming agent satisfyingconditions of: application temperature of conductive adhesiveagent<melting temperature of micro-capsule; melting temperature ofmicro-capsule≦hardening temperature of binder resin; and activationtemperature of chelating agent≦hardening temperature of binder resin. 6.The conductive adhesive agent according to claim 1, wherein said elutionpreventing film-forming agent is made of a water-insoluble material. 7.The conductive adhesive agent according to claim 1, wherein said elutionpreventing film-forming agent is made of such a material that isinsoluble in an aqueous solution containing hydrogen sulfide or sulfuroxide.